The present invention relates to a continuous method of producing propylenecarbonate in a reaction of propylene oxide with carbon dioxide in presence of phthalocyanine catalysts in accordance with the scheme:
The development of ecologically safe and highly efficient method for producing propylenecarbonate is an important task, since it is a raw material for obtaining of a new generation polymer, namely polypropylenecarbonate.
Polypropylenecarbonate is a polymer which is used for producing laser disks, control panels in cabins of modern airplanes. It has unique strength properties, long service life and fire resistance. The technology of its manufacture nowadays is very expensive and not sufficiently developed.
A raw material for producing polypropylenecarbonate is propylene oxide. Propylene oxide is characterized by linking reactions, which are enhanced by a relative easiness of opening of the cycle. The most used reaction is hydration with formation of propyleneglycol and also di-, tri- and polyglycols as byproducts. The hydration of propylene oxide with the use of CO2(120-160° C., 0.5-4 MPa) is performed selectively with formation of monopropyleneglycol; an intermediate product is propylene carbonate.
Reactions of alkylene oxides and carbon dioxide in presence of catalysts are known and disclosed in U.S. Pat. Nos. 2,773,070; 2,873,282; 3,535,341; 4,786,741; European patent no 0297647, and Japanese patent no. 63-181765.
As a rule, it was proposed to use as catalysts for reactions in substantially high concentrations-halogen-containing compounds, whose use led to production of alkylene carbonates, that contain a great quantity of halogen-containing admixtures. In addition, the majority of proposed catalysts loose their activity in these reactions or contribute to interaction of epoxydes with each other, and not with carbon dioxide. It is therefore necessary to use catalysts, which are not destroyed in the process of linking of carbon dioxide, do not introduce impurities into reaction products, and allow to efficiently link carbon dioxide.
A method of producing alkaline carbonates with the use of phthalocyanines of metals as catalysts is disclosed in U.S. Pat. No. 5,283,356.
This method has the disadvantage of low solubility of the used catalysts, which leads most probably to hetergenous course of the process with a significantly lower efficiency. Moreover, conducting the reaction in hetergenous conditions does not allow to achieve quantitative linking of carbon dioxide, which correspondingly significantly reduces the efficiency of the method.
This disadvantage was eliminated with the use of tert-butyl-substituted phthalocyanine complexes as catalysts, whose solubility is several orders higher than solubility of its non-substituted analogs, as disclosed in patent no. 2,100,355 of Russian Federation.
This method however, as all above mentioned methods, require to conduct experiments in static and significantly hard conditions, in particular in an autoclave with temperature 180° C. during two hours. Moreover, the used catalyst did not have a significantly expanded surface, that reduced the reaction and led to fast poisoning of the catalyst.
A continuous method of producing of polypropylenecarbonate in presence of the phthalocyanine catalysts by carboxylation of propylene oxide was proposed with the use of an inert carrier, in particular granulated adsorbent celite 535, which has the following characteristics: chemical composition-silicium acid with low quantity of oxides Al, Fe, Mg, Ca, specific surface 1-3 m2/g, particulate density approximately 0.24 g/cm3, average pore diameter 1-3 μm, granule diameters 60-80 mesh. As a catalyst tert-butyl substituted phthalocyanine aluminum chloride PctAlCl or its non-substituted analog PcAlCl were used. The reaction was conducted in a temperature range of 100-150° C., with a pressure in a reactor 20-40 atm. The supply of C02 (gas) was 12 g/hour, of propylene oxide 0.1 g/hour. Mol ratio C02/propylene oxide was approximately 144/1. Time of conducting the process until complete loss of catalyst activity was 16-24 hours. Average yield during the time of conducting the reaction was 2-7% of propylenecarbonate relative to a mass of propylene oxide, depending on used catalyst. It is disclosed in patent no. 2,228,933 of Russian Federation.
This method however requires a frequent change of the spent catalyst, and the yield of the final product and process of linking of carbon dioxide did not satisfy the conditions of modern manufacture.